Sensitive electrophotographic plates

ABSTRACT

VERY SENSITIVE ELECTROPHOTOGRAPHIC PLATES ARE PROVIDED HAVING A CHARGE GENERATING LAYER COMPRISING A SQUARIC ACID METHINE DYE AND A CHARGE TRANSPORT LAYER COMPRISING A TRI-ARYL PYRAZOLINE COMPOUND.

3,824,099 SENSITIVE ELECTROPHOTOGRAPHIC PLATES Robert Bruce Champ and Meredith David Shattuck, San

Jose, Calif., assignors to International Business Machines Corporation, Armonk, N .Y. No Drawing. Filed Jan. 15, 1973, Ser. No. 323,678 Int. 'Cl. G03c 5/06 US. CI. 96-15 4 Claims ABSTRACT OF THE DISCLOSURE Very sensitive electrophotographic plates are provided having a charge generating layer comprising a squaric acid methine dye and a charge transport layer comprising a tri-aryl pyrazoline compound.

FIELD OF THE INVENTION The present invention is concerned with electrophotographic plates. In particular, it is concerned with layered plates having a charge generation layer and a separate charge transport layer. The charge generation layer comprises a squaric acid methine dye and the charge transport layer comprises a tri-aryl pyrazoline compound. Electrophotographic plates containing these layers have been found to be extremely sensitive to light.

PRIOR ART Squaric Acid methine dyes are known compounds which have been described in the literature. 1,3- and 1,2-squaric acid methine dyes, both of which are useful in the present invention, have been described, for example, in US. Pat. 3,617,270 where methods for their synthesis are also described. That patent discloses the use of squaric acid methine dyes for the optical sensitization of zinc oxide, in which use the squaric acid methine dye is used at a concentration of about 0.1 to 20 milligrams per square meter of finished photoconductive layer.

SUMMARY OF THE INVENTION The electrophotographic plates of the present invention comprise, in addition to a conductive substrate, a charge generating layer containing a squaric acid methine dye and a separate charge transport layer containing a tri-aryl pyrazoline compound. Electrophotographic plates having the structure recited above have been found to be extremely fast in their response to light. They are panchromatic out to about 7000 Angstrom units. They are also responsive to light having wave lengths up to 9000 Angstroms. A particularly suitable field for their use is with lasers having wave lengths of from about 8000 to about 9000 Angstrorns.

To obtain the high sensitivities of the present invention it is necessary that the electrophotographic plates contain both squaric acid charge generating material and tri-aryl pyrazoline charge transporting material. Both are essential elements of the present invention. This result was totally unexpected and the theoretical explanation for it is not known.

The use of tri-aryl pyrazoline containing charge transport layers is disclosed in US. Patent Application Ser. No. 323,677, filed on even date herewith.

There are several well known electrophotographic reproduction processes in current use. They differ in the particular way in which they are carried out, particularly United States Patent 0 ice in the sequence in which electric charging (usually with a corona) and illumination are carried out. All electrophotographic reproduction processes, however, involve the process step of selectively rendering portions of a photoconductor electrically conductive by selective exposure to light. The electrophotographic plates of the present invention are useful in all such processes.

In the electrophotographic plates of the present invention, the charge transport layer may be used either on top of the charge generating layer, or beneath the charge generating layer. For mechanical reasons, it is generally preferred that the charge transport layer be on top. The charge transport layer may vary considerably in thickness, in general being from about 10 to about 30 microns thick, preferably from about 15 to about 25. When the charge transport layer is on top of the charge generating layer, i.e. when the charge generating layer is between the charge transport layer and the conductive substrate, the electrophotographic plate should be charged negatively. In those instances where the charge transport layer is beneath the charge generating layer, that is, when the charge transport layer is between the charge generating layer and the conductive substrate, the electrophotographic plate should be charged positively.

In forming the charge generating layers of the present invention, the squaric acid methine dye maybe used alone, but it is preferred to use a squaric acid methine dye in conjunction with a binder when the layer is formed by coating from a slurry. The optimum ratio of dye to binder, depending upon the particular dye, is generally from about 0.1 to about 0.9. Binderless layers may be formed by vacuum evaporation. Many types of binder materials, such as resins, are known to the prior art. Many polyesters are suitable materials. Sucrose benzoate may also be employed in many mixtures of the various, binders. Particularly outstanding results have been obtained using polyvinyl butyral. In general, it is preferred that the charge generating layer be from about 0.1 to about 2 microns thick, most preferably about 0.5 microns. It is also preferred that the charge generating layer contain from approximately 50 to about 100 milligrams of the squaric acid methine dye per square meter of plate area.

The following examples are given solely for purposes of illustration and are not to be considered limitations on the invention, many variations of which are possible without departing from the spirit or scope thereof.

EXAMPLES l.-8

The following squarylium pigments were all ground to a fine particle size in tetrahydrofuran and applied by a knife blade coater on aluminized Mylar substrate. (Mylar is a trade name for polyethyleneterephthalate film from Dupont.) The coating percent solids is 3% and the wet gap setting is one mil. Over this generation layer is then coated a transport layer of 2 parts Merlon 60 and 1 part DEASP by weight. Coating thickness is 13-15 microns thick. Merlon 60 is a trade name for a polycarbonate resin marketed by Mobay Chemicals. DEASP is a shortened abbreviation for 1-Phenyl-3-[pdiethylaminostyryH-S [p-diethylamino phenyl]-pyrazoline. The coated films are then heated for 30 minutes electrometer. The illumination was from a tungsten halogen lamp, watts, 28 volts at a distance of approximately .5 cm.

Light decay E Charge (mlcrojoules/ acceptance Example number Pigment cmfl) (volts) OH Et Et Et Et 580 a on 0H -Q 0H H Me Me N +2 N Me Me OH OH 0 2.2 670 6..--:--.-.: OH OH OH OH on. on 0 on OH:

HO- OH l CH3 HI E- A; is the amount of energy required to decay the photoconductor by exposure to light to one-half its charge acceptance.

EXAMPLE 9 One gram of the compound CH; 0- CH3 CH3 /CH; J K

is ground in a McCrone micronizing mill for minutes whereupon 3 g. of 5% polyvinylbutyral (XYHL B-800 from Union Carbide) is added with 7 g. of tetrahydrofuran. The material is micronized for 20 minutes and then decanted into a jar. Seven grams of a 5% Elvacite 4.05 g. Merlon 60 2.7 g. DEASP.

8 d.p.s. 10% DC-200 (Dow Corning Silicon Oil) in tetrahydroforan.

The percent solids is 15.5 and the coating speed is 8 f.p.m. The fihn is treated for 15 minutes at 115 C.

Sensitometry on the above film gave the following data:

Dark Decay v./Sec 40 volts/sec. E from 700 v. charge [Photocopy green lamps (PCG)] 0.95 microjoules/cmF. Dark Charge with 650 Volts on Screen 780 v.

EXAMPLE 10 When the compound O CH3 1 CH3 @GK (JR/3 3 OH:

is employed in the above formulation and coated to an optical density of 0.2 to green light the following sensitometric results are obtained:

Dark Decay Volts/sec. 220 volts/sec. E from 700 v. charge (PCG) 0.58 microjoules/cmF. Dark charge with 780 v. on

Screen 800 v.

EXAMPLE 11 When the compound OH O- OH is employed in the formulation as described in Example 9 and coated to an optical density of 0.6 to .green light the following sensitometric results are obtained:

Dark Decay Volts/sec. 16 volts/sec. E from 700 v. charge (PCG) 0.74 microjoules/cmF. Dark charge with 720 v. on

screen 780 v.

EXAMPLE 12 When the formulation of Example 9 is coated on aluminized Mylar which has been subbed with a coating of 0.3;]. of an acrylic resin (A-11 from Roehm and Haas) the following sensitometric data are noted:

Dark Decay v./sec. v./sec. E from 700 v. charge PCG) 1.1microjoules/cmfi. Dark charge with 680 v. on

screen 750.

EXAMPLE 13 The charge generating layer was prepared by evaporating the compound in Example 11 on an aluminized Mylar substrate to an optical density to green light of 0.4.

This was coated with a transport layer consisting of:

Parts Polyester (Vitel PE-200 from Goodyear) 2 DEASP 1 The percent solids is 20 in tetrahydrofuran and the coating speed is about 8 f.p.m. The film was dried to remove excess solvent at C. for 30 minutes.

Sensitometry on the above film is as follows:

Dark Charge 700 v. Energy required to decay to 200 v. (Photocopy green lamp) 0.4 microjoules/cmf".

References Cited UNITED STATES PATENTS 3,617,270 11/1971 Kampfer 96-l.7 3,527,602 9/1970 Fox 961.5 3,634,135 1/1972 Osaka 961.5

FOREIGN PATENTS 4,326,710 11/1968 Japan 961.6

RONALD H. SMITH, Primary Examiner J. L. GOODROW, Assistant Examiner US. Cl. X.R. 961.8, 1.6

. UNITED STATES PATENT OFFICE 1 CERTIFICATE OF CRRECTION Patent no. 3,824,099 Dated Julv 16,4374

Inventor(3) Robert Bruce Champ et al It is certified that error appears in the above idantitied patent and that said Letters Patent hereby untreated as shown aalowz r' In the Claims, Claim 1 should read as follows:

1. An electrophotographic plate comprising a conductive substrate, a layer comprising a squaric acid methine dye and a separate layer comprising a tri-aryl pyrazoline compound.

Signed and sealed this 22nd day of October 1974.

(SEAL) Attest:

McCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents 

